Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$121.39	3.675%	$125.8511	$125.85	$125.85	$125.90
Purchase #2	$129.92	7.272%	$139.3678	$139.37	$139.35	$139.40
Purchase #3	$208.86	13.752%	$237.5824	$237.58	$237.60	$237.60
Purchase #4	$228.90	9.273%	$250.1259	$250.13	$250.15	$250.10
Purchase #5	$96.34	13.255%	$109.1099	$109.11	$109.10	$109.10
Purchase #6	$110.40	4.612%	$115.4916	$115.49	$115.50	$115.50
Purchase #7	$82.77	3.274%	$85.4799	$85.48	$85.50	$85.50
7 purchase totals =	$978.58		$1,063.0086	$1,063.01	$1,063.05	$1,063.10